Import libcds.

[SXSI/libcds.git] / src / static_bitsequence / table_offset.h

diff --git a/src/static_bitsequence/table_offset.h b/src/static_bitsequence/table_offset.h
new file mode 100644 (file)
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+++ b/src/static_bitsequence/table_offset.h
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+/* table_offset.h
+ * Copyright (C) 2008, Francisco Claude, all rights reserved.
+ *
+ * Table for offsets definition.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ *
+ */
+
+#ifndef _TABLE_OFFSET_H
+#define        _TABLE_OFFSET_H
+
+#include <basics.h>
+#include <iostream>
+
+//using namespace std;
+
+/** Universal table required for static_bitsequence_rrr02, Raman, Raman and Rao's [1] 
+ *  proposal for rank/select capable data structures, it achieves space nH_0, 
+ *  O(sample_rate) time for rank and O(log len) for select. The practial implementation 
+ *  is based on [2]
+ * 
+ *  [1] R. Raman, V. Raman and S. Rao. Succinct indexable dictionaries with applications 
+ *     to encoding $k$-ary trees and multisets. SODA02.
+ *  [2] F. Claude and G. Navarro. Practical Rank/Select over Arbitrary Sequences. SPIRE08.
+ *
+ *  @author Francisco Claude
+ */
+class table_offset {
+
+public:
+  /** builds a universal table, designed for u<=15 */
+       table_offset(uint u);
+       ~table_offset();
+       
+       /** Increments the counter of users for the table */
+       inline void use() {
+               users_count++;
+       }
+       
+       /** Tells the object that the user is not going to need the table anymore. */
+       inline table_offset * unuse() {
+               users_count--;
+               if(!users_count) {
+                       delete this;
+      return NULL;
+    }
+    return this;
+       }
+       
+       /** Computes binomial(n,k) for n,k<=u */
+       inline uint get_binomial(uint n, uint k) {
+               return binomial[n][k];
+       }
+       
+       /** Computes ceil(log2(binomial(n,k))) for n,k<=u */
+       inline ushort get_log2binomial(uint n, uint k) {
+               return log2binomial[n][k];
+       }
+       
+       /** Returns the bitmap represented by the given class and inclass offsets */
+       inline ushort short_bitmap(uint class_offset, uint inclass_offset) {
+               if(class_offset==0) return 0;
+               if(class_offset==u) return (ushort)(((uint)1<<u)-1);
+               return short_bitmaps[offset_class[class_offset]+inclass_offset];
+       }
+       
+       /** Returns u */
+       inline uint get_u() {
+               return u;
+       }
+       
+       /** Computes the offset of the first u bits of a given bitstring */
+       inline ushort compute_offset(ushort v) {
+               return rev_offset[v];
+       }
+       
+       /** Returns the size of the bitmap in bytes */
+       uint size();
+
+protected:
+       int users_count;
+       uint u;
+       uint ** binomial;
+       ushort * rev_offset;
+       ushort ** log2binomial;
+       ushort * offset_class;
+       ushort * short_bitmaps;
+       
+       void fill_tables();
+};
+
+#endif